Time-resolved structure determinations are at the forefront of attempts to understand the mechanisms of protein reactions. We have demonstrated a system for collecting high quality x-ray absorption spectroscopy data on microsecond timescales. The method can be used for both full spectra accumulation and kinetic spectro-photometry. This system has been used to examine the formation of [unreadable]triplet[unreadable] states in zinc and platinum substituted proto- and octaethyl prophyrins, where the excited state structure is of intense theoretical interest. Preliminary data show little structural change in the excited state, implying only minor movement of the metal out of the porphyrin plane upon photo-excitation.